As the leading cause of preventable death in the United States, cigarette smoking represents a serious public health concern. A majority of smokers consistently report that they smoke to relieve anxious mood. However, research on the relationship between anxious mood and smoking behavior is very sparse, has been conducted primarily in artificial laboratory settings, and has yielded conflicting results;consequently, it offers only limited and situation-specific evidence for the anxiety-reducing properties of smoking. The ultimate goal of the proposed program of research is to improve smoking prevention and cessation interventions by elucidating the mechanisms of interaction between anxious mood and smoking behavior. The specific aims of the proposed study are to test in a naturalistic setting whether (1) anxious mood predicts cigarette smoking. (2) smoking relieves anxious mood, and (3) certain individual characteristics influence the relationship between anxious mood and smoking. The proposed study will employ ecological momentary assessment techniques to fulfill these specific aims. Adult smokers will carry personal digital assistants (PDAs) with them at all times during two separate one-week periods of assessment. During these assessment periods, participants will record their levels of anxious mood and their smoking behavior on their PDA whenever they smoke a cigarette, and when they are prompted by their PDA to complete an assessment at random intervals. Participants will also complete a series of self-report questionnaires at baseline that measure individual traits, such as level of depressed mood and the strength of their beliefs that smoking will relieve anxiety, which will be evaluated as potential predictors of the relationship between anxious mood and smoking behavior. This procedure will provide a prospective, longitudinal, time-sensitive record of the relationship between anxious mood and smoking behavior in the smokers'natural environment. The results of the proposed study will enable us to construct a strong, empirically grounded theoretical model of anxious mood and smoking, which can then be used to inform public health models of smoking intervention. Our findings will improve our ability to identify anxious populations that are particularity at risk for cigarette smoking and develop more effective smoking prevention and cessation programs that directly target anxious mood as a potential trigger for smoking behavior. By improving smoking intervention programs, we aim to reduce smoking rates in the U.S. and the steep health-related and economic costs that are incurred at the individual, community, and national level as a consequence of cigarette smoking.